Juniper would be the best plant to use as a hedge barrier. Juniper comes in an array of varieties. It can be kept as short as a few feet or at tall to tower over housing. It grows very thick, with waxy needles, perfect for blocking out sound.
Hedges can be used as sound barriers. But they are not a panacea for noise reduction. For best results you should probably choose hedges that grow up, rather than out. Evergreens grow tall quickly and help to reduce sound. Try using cedars and pines for more effective noise reduction. Certain hedge poplars are also a favorite.
Yes, because not only are plants great at naturally sound proofing a building, but they have other advantages such as they are completely natural, inexpensive, and can serve as beautiful decoration.
A Hedge will only work if they are at a certain height and size if you have full grown ones I would say yes, if you will have full grown ones put in place. Or if you can allow them to grow and the type you choose to put in
Using hedges for sound barriers is a great idea if you have the room and time for annual upkeep. American arborvitae, canadian hemlock, and white pines will grown in most of the united states.